Fluted projectile points in a stratified context at the Raven Bluff site document a late arrival of Paleoindian technology in northwest Alaska: BUVIT et al.

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Our understanding of the northern fluted point tradition, a critical early New World lithic assemblage, is constrained by limited data from stratified, datable contexts. Here, we report on the Raven Bluff site in northwest Alaska, where fluted projectile points, microblades, and a well‐preserved faunal assemblage have been recovered from datable sediments. Results show that prehistoric inhabitants occupied a stone‐sorted polygon where retooling, game processing, and raw material procurement occurred mostly between 12,720 and at least 11,340 cal. yr B.P. We argue that once polygon formation ended, the stratigraphic context remained relatively intact. Further studies focused on the site’s lithic and bone assemblages will help shape our understanding of the relationship between fluted point technology, microblades, and caribou hunting in northern Alaska.

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... While it seems possible that the biface and skull are associated, and represent evidence of the human occupation of now flooded coastal margins on the continental shelf during the LGM, the lack of a scientific investigation of the site together with the alternative possibilities (among others) that the finds are contextually unrelated or a product of ice-rafted debris, precludes widespread acceptance of the site's validity. The dating of these pre-Clovis-aged sites south of the continental ice sheets, combined with recognition that Clovis sites date oldest in the U.S. Plains/Southwest region and youngest in Alaska (Goebel et al., 2013;Buvit et al., 2018), have finally laid the CFH to rest. ...
... During the twentieth century, archaeologists sought to identify a technological progenitor for the CPT among late Pleistocene-aged Beringian and Northeast Asian sites (Bonnichsen and Schneider, 1999;Goebel, 2004) and the report of a potential (but later dismissed) fluted point in western Beringia sparked great interest within the First American studies community (King and Slobodin, 1996). The later discovery that Alaskan fluted points post-dated fluted point technology south of the North American continental ice sheets (Goebel et al., 2013;Buvit et al., 2018) was perhaps the last straw and confirmed that Clovis fluted points were not the earliest lithic technology of the Americas. Given these developments, most archaeologists appear to consider the CPT as a North American innovation and interest has shifted to uncovering details about the "Proto-Clovis" ancestor to the CPT (e.g., Ferring, 2012;Haynes, 2002Haynes, , 2015Jennings and Waters, 2014). ...
The presence of well-documented sites in the Americas predating and south of the opening of an ice-free corridor in the North American ice sheets lends credence to a Pacific coastal migration theory (CMT) explaining the route for the initial peopling of the Americas. This theory has been informally discussed for more than 50 years, but until recently, has been largely ignored and never properly defined as a result. We provide a formal definition of the CMT which, briefly stated, is that Upper Paleolithic populations moved from Asia to coastal regions along the northwestern Pacific Rim between ~45-30 ka. By ~30 ka these coastal populations developed a mixed maritime, nearshore, and terrestrial adaptation involving the use of boats, shell fishhooks for deep-water fishing, and a stemmed point and macroblade core technology. About 25-24 ka a subset of these coastal populations became isolated somewhere in the vicinity of the Japan/Paleo-Hokkaido, Sahkalin, Kuril (PSHK) region, developing genetically into the ancient Native American (ANA) populations that eventually settled the Americas. Between ~22-16 ka these ANA people began migrating by foot and boat along the southern Beringian coast and down the Alaskan and Canadian coastline into the Americas south of the continental ice sheets before eventually expanding inland. We develop a series of testable hypotheses through which the CMT can be examined.
... Thus far, the search for a cultural progenitor linking the archaeological LUP societies of NE Asia with a lithic technology found in the earliest sites in the Americas has primarily focused on higher latitude Beringian and Siberian sites (Goebel, 2004). Building from archaeological evidence available at the time, the original expectation was that a NE Asian cultural progenitor of the First Americans should bear close technological resemblance to the Clovis Paleoindian Tradition [CPT] (Bonnichsen & Schneider, 1999;Goebel, 2004); however, fluted points have not been found in NE Asia or western Beringia and fluted points in eastern Beringia are clearly younger than those from CPT sites found south of the North American continental ice sheets (Buvit et al., 2018;Goebel et al., 2013). Later, this model shifted toward an expectation that the First Americans should possess a lithic technology that looked something like the Nenana Complex, which predates the CPT and has been compared more readily with LUP cultural patterns in western Beringia and central Siberia (e.g., Goebel et al., 1991). ...
... Fluted points have been found in Alaska, but they appear to be late; the earliest date is ca. 10,700 rcbp (12,700 cal BP) from Raven Bluff (Buvit et al. 2019), and there are several dates of ca. 10,200 rcbp (11,800 cal BP) from Serpentine Springs on the Seward Peninsula (Smith and Goebel 2018). ...
The study of the peopling of the Americas has been transformed in the past decade by astonishing progress in paleogenomic research. Ancient genomes now show that Native American ancestors were formed in Siberia or the Amur region by admixture of ca. 15–30% Ancient North Eurasian genes with those of East Asians. The Anzick infant, buried with Clovis bifaces at 12,900 cal BP, belonged to a group that was ancestral to later Native Central and South Americans. Fishtail points, derived from Clovis, mark the arrival and rapid expansion of Clovis-descended Paleoindians across South America, also evident in the sharp increase of radiocarbon dates, continent-wide, at 13,000–12,500 cal BP. In both North and South America, extinction of most genera of megafauna was virtually simultaneous with Paleoindian expansion. Human hunting must have been involved, perhaps in concert with other indirect impacts. Contrary to the alternative bolide impact theory, there is no evidence of a dramatic human population decline after 12,800 cal BP. Ancient genomes show that divergent lithic traditions after 13,000 cal BP need not be attributed to a separate Pacific Rim migration stream. Several recent finds raise the possibility that pre-Clovis people might have reached the Americas before 20,000 cal BP, but these precursors must have either failed to thrive, or were ultimately replaced by proto-Clovis or Clovis people. Consilient paleogenomic and archaeological data indicate that initial colonization by Paleoindian ancestors of living Native Americans occurred after 14,500 cal BP.
... Characterized by their morphological richness and diversity, projectile points are one of the most remarkable lithic materials of the PaleoAmerican archaeological record from both hemispheres in the New World. From Alaska to Tierra del Fuego, in its northernmost and southernmost points respectively, a great quantity of stemmed and lanceolate patterns were employed by the early occupants of the Americas (e.g., Bird 1969;Buvit et al. 2018;Erlandson and Braje 2015;Flegenheimer and Weitzel 2017;Flegenheimer, Miotti, and Mazzia 2013;Hermo, Terranova, and Miotti 2015;Jennings, Smallwood, and Waters 2015;Mazzanti et al. 2013;Méndez et al. 2018;Nami 2014a;Smith and Goebel 2018;Suarez 2015). An interesting pattern in their distribution, however, is that in contrast to the record of PaleoAmerican points north of the Río Grande in North America, towards the south they are reduced to only a small number of shapes (e.g., Bryan 1983;Chauchat et al. 1988;Dillehay et al. 2015;Maggard 2015). ...
Early projectile points frequently referred to as “fishtails” or “Fell” are found from northern Mesoamerica to the southern tip of South America. Becoming a widespread PaleoAmerican marker spanning ∼11,000–10,000 radiocarbon years ago, these points are found in the highest concentration in the Southern Cone of South America. To continue documenting and adding data on this topic, in this brief report we present morpho-technological observations on six specimens recently documented in the Republics of Uruguay and Argentina. The points in this sample resemble other Fell points in their general shape, straight and rounded shoulders, resharpening, and overall dimensions.
... These have predominantly consisted of exhausted and discarded fluted-point fragments at the end of their use lives (Smith and DeWitt 2016). In 2005 and 2007 two sites in western Alaska, Serpentine Hot Springs and Raven Bluff, finally provided buried and dateable contexts for Northern Fluted points mutually supporting a Younger Dryas age (Buvit et al. 2018;Goebel et al. 2013;Hedman 2010). A "preform" was reported from Raven Bluff, and both sites provided discarded fluted-point fragments associated with debitage. ...
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Recent research has begun to shed light on the role the Northern Fluted Complex (NFC) played in the peopling of the Americas. Our understanding of NFC chronology and origins has increased with the discovery of new sites with buried and datable fluted-point components and digital means of morphological and technological continent-wide analyses. However, we have had few opportunities to observe examples of NFC points discarded early in the manufacturing process, hindering our understanding of NFC technology and, ultimately, Paleoindian behavior in the North. To resolve this problem, this research contributes a hypothesis of the NFC manufacture process developed from examination of exhausted fluted-point fragments and the addition of a small collection of artifacts that potentially represent earlier stages in the NFC reduction continuum. Flaking Index is used to identify the appropriate placement of artifacts in the reduction sequence. Experimental replication of NFC points is used to test the production sequence hypothesis.
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For decades archaeologists have debated whether Paleolithic humans withdrew from Northeast Asia during the Last Glacial Maximum (LGM), an issue with especially important implications for the Pleistocene peopling of Siberia, Beringia, and the Americas. Evidence suggests a major population contraction occurred in all three areas around the time of the global LGM between around 26,000 and 20,000 cal BP. For one, gaps exist in prehistoric 14 C records that separate older sites with no wedge-shaped microblade cores from younger sites with this distinctive technology. Also, variation between actual and simulated distributions of dates indicates periods of abandonment through time rather than continuous occupation. The maritime region of Sakhalin and Hokkaido, in contrast, may have experienced population expansion when the islands were connected to mainland Asia as part of a peninsula. It is further possible that the genetic split between Paleo Siberians and ancestral Native Americans can be traced archaeologically through the distribution of wedge-shaped microblade core technology from the coastal zones back into interior regions following each population contraction. Finally, if humans retreated from a greater part of Northeast Asia at the LGM, then a genetic standstill in Beringia or Siberia is difficult to reconcile.
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The central lowland of Beringia (aka the Bering land bridge) has been viewed alternately as a barrier or a refugium to the Native American founder population during the Last Glacial Maximum (LGM). Here we suggest that an equally – if not more – likely LGM home for the founder population is the arctic zone of Beringia. People were drawn to eastern arctic Beringia during the post-LGM Younger Dryas (YD) cold period and occupied western arctic Beringia during the cold interval preceding the LGM (GS5/HE3). Arctic Beringia probably contained adequate resources for an LGM human population, especially across the exposed East Siberian Arctic Shelf (“Northwest Beringian Plain”), which supported an extensive steppe-tundra habitat populated by mammoth and other large mammals before and during the LGM. An arctic Beringian refugium would explain a growing body of evidence that indicates an early (or pre-) LGM divergence of the Native American founder population from its Asian source.
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The central lowland of Beringia (aka the Bering Land Bridge) has been viewed alternately as a barrier or a refugium to the Native American founder population during the Last Glacial Maximum (LGM). Here we suggest that an equally—if not more—likely LGM home for the founder population is the arctic zone of Beringia. People were drawn to eastern arctic Beringia during the post-LGM Younger Dryas (YD) cold period, and occupied western arctic Beringia during the cold interval preceding the LGM (GS5/HE3). Arctic Beringia probably contained adequate resources for an LGM human population, especially across the exposed East Siberian Arctic Shelf (Northwest Beringian Plain), which supported an extensive steppe-tundra habitat populated by mammoth, horse, and other large mammals before and during the LGM. An arctic Beringian refugium would explain a growing body of evidence that indicates an early (or pre-) LGM divergence of the Native American founder population from its Asian source.
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Forty years ago, Knut Fladmark (1979) argued that the Pacific Coast offered a viable alternative to the ice-free corridor model for the initial peopling of the Americas—one of the first to support a “coastal migration theory” that remained marginal for decades. Today, the pre-Clovis occupation at the Monte Verde site is widely accepted, several other pre-Clovis sites are well documented, investigations of terminal Pleistocene subaerial and submerged Pacific Coast landscapes have increased, and multiple lines of evidence are helping decode the nature of early human dispersals into the Americas. Misconceptions remain, however, about the state of knowledge, productivity, and deglaciation chronology of Pleistocene coastlines and possible technological connections around the Pacific Rim. We review current evidence for several significant clusters of early Pacific Coast archaeological sites in North and South America that include sites as old or older than Clovis. We argue that stemmed points, foliate points, and crescents (lunates) found around the Pacific Rim may corroborate genomic studies that support an early Pacific Coast dispersal route into the Americas. Still, much remains to be learned about the Pleistocene colonization of the Americas, and multiple working hypotheses are warranted.
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The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ĝ1/4 53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into the Arctic Ocean, mollusc and insect fossils and paleobotanical data) have suggested a range of ages for the Bering Strait reopening, mainly falling within the Younger Dryas stadial (12.9-11.7 cal ka BP). Here we provide new information on the deglacial and post-glacial evolution of the Arctic-Pacific connection through the Bering Strait based on analyses of geological and geophysical data from Herald Canyon, located north of the Bering Strait on the Chukchi Sea shelf region in the western Arctic Ocean. Our results suggest an initial opening at about 11 cal ka BP in the earliest Holocene, which is later than in several previous studies. Our key evidence is based on a well-dated core from Herald Canyon, in which a shift from a near-shore environment to a Pacific-influenced open marine setting at around 11 cal ka BP is observed. The shift corresponds to meltwater pulse 1b (MWP1b) and is interpreted to signify relatively rapid breaching of the Bering Strait and the submergence of the large Bering Land Bridge. Although the precise rates of sea level rise cannot be quantified, our new results suggest that the late deglacial sea level rise was rapid and occurred after the end of the Younger Dryas stadial.
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In northeastern Beringia, the area today made up of northern Alaska (USA) and Yukon (Canada), archaeologists typically refer to the earliest archaeological assemblages dominated by bifacial technology as “Northern Paleoindian.” These assemblages mostly date to during and immediately after the Younger Dryas cold period, 12,900–11,200 calendar years ago, although at least one and possibly three occupations pre-date 13,000 calendar years ago and rival Clovis in age. Distinctive lanceolate bifacial points dominate these assemblages; variation in size, shape, production technique, and basal treatment of these points has led archaeologists to define three assemblage groups, the fluted-point, Mesa, and Sluiceway complexes. These projectile points were components of technological systems that emphasized high-quality lithic raw materials used in a formal bifacial industry. Scarce faunal remains and other evidence suggest a subsistence regime centered on the hunting of herd animals such as caribou and bison, and land-use patterns characterized by seasonally structured movements and high logistical mobility. Standardized wedge-shaped core and microblade technology has not been unequivocally tied to the Northern Paleoindian complexes, giving them a character different from most other early Beringian sites and more strongly suggesting a link to late-Pleistocene technocomplexes in the midcontinent. However, careful technological and morphometric studies are needed to assess the relationship of these early northern Beringian industries to those of like age in the temperate latitudes of North America. © 2014 by Kelly E. Graf, Caroline V. Ketron, and Michael R. Waters. All rights reserved.
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While bison were the most abundant large mammals in Eastern Beringia for most of the last 100 000 years, their range declined drastically at the end of the Pleistocene and through the Holocene. Research into the nature of Holocene human interactions with bison suffers from scarcity of faunal remains from most archaeological sites and poor chronological control of paleontological specimens over broad areas of Eastern Beringia. We examined the dating, context, and identification of purported bison bones spatially associated with two late prehistoric archaeological sites in northern Alaska to contribute to a better understanding of bison biogeography and the possible role of these large mammals in prehistoric economies. We confirmed the presence of two bison bones from the 17th century Kangiguksuk archaeological site (49-XBM-012) in northwestern Alaska, but radiocarbon dates older than 30 000 14C years BP for both bones demonstrate that those bison were not hunted by the site occupants. From the Lakeside site (49-KIR-275) in the central Brooks Range, a bone reported to be bison and dated to about 2400 14C years BP was shown through DNA sequencing to be moose (Alces alces). We point to a large set of dated bison specimens from Alaska's Arctic Slope that suggests bison were locally extinct in north-central and northwestern Alaska by the beginning of the Holocene and were subsequently unavailable to human hunters in that region.
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We present a new common stratigraphic timescale for the North Greenland Ice Core Project (NGRIP) and GRIP ice cores. The timescale covers the period 7.9–14.8 kyr before present and includes the Bølling, Allerød, Younger Dryas, and early Holocene periods. We use a combination of new and previously published data, the most prominent being new high-resolution Continuous Flow Analysis (CFA) impurity records from the NGRIP ice core. Several investigators have identified and counted annual layers using a multiparameter approach, and the maximum counting error is estimated to be up to 2% in the Holocene part and about 3% for the older parts. These counting error estimates reflect the number of annual layers that were hard to interpret, but not a possible bias in the set of rules used for annual layer identification. As the GRIP and NGRIP ice cores are not optimal for annual layer counting in the middle and late Holocene, the timescale is tied to a prominent volcanic event inside the 8.2 kyr cold event, recently dated in the DYE-3 ice core to 8236 years before A. D. 2000 (b2k) with a maximum counting error of 47 years. The new timescale dates the Younger Dryas-Preboreal transition to 11,703 b2k, which is 100–150 years older than according to the present GRIP and NGRIP timescales. The age of the transition matches the GISP2 timescale within a few years, but viewed over the entire 7.9–14.8 kyr section, there are significant differences between the new timescale and the GISP2 timescale. The transition from the glacial into the Bølling interstadial is dated to 14,692 b2k. The presented timescale is a part of a new Greenland ice core chronology common to the DYE-3, GRIP, and NGRIP ice cores, named the Greenland Ice Core Chronology 2005 (GICC05). The annual layer thicknesses are observed to be log-normally distributed with good approximation, and compared to the early Holocene, the mean accumulation rates in the Younger Dryas and Bølling periods are found to be 47 ± 2% and 88 ± 2%, respectively.
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The soils under larch forests of northeastern Yakutia are described. Particular emphasis is given to the relationships between soils and local topography. The results of chemical and particle-size distribu-tion analyses of the most widespread soils are presented. The approaches to forecasting the evolution of soil and vegetation cover under the impact of global climate changes are formulated.
Intensive Paleoindian occupation of the Mesa site occured between 10,300 and 9700 14C yr B.P. Was the timing of this occupation controlled by environmental changes? We investigated stratigraphic records of geomorphology and vegetation to describe how landscapes in the Arctic Foothills changed between 13,000 and 8000 14C yr B.P. Paleoindians were present during a time of rapid and sweeping changes in vegetation, slope erosion, floodplain dynamics, permafrost stability, and soil type. We speculate that Paleoindians moved into arctic Alaska to exploit population highs in large ungulates that in turn were triggered by landscape-scale, geomorphic disturbances caused by climate changes. Environmental changes slowed and rising sea levels flooded Alaska's continental shelves during the Early Holocene, causing summer temperatures to fall and precipitation to increase. A more stable climate and the prevalence of maritime air masses allowed the spread of tussock-tundra vegetation, which probably drove both the Paleoindians and their prey species out of the region.
Influence of topography, soils, and vegetation on the microclimate and hydrology of four slopes and a plateau site located within a 1-km2 area in the continuous permafrost zone of Arctic Canada was studied. The field season covered two summers with contrasting climatic conditions. During the warm, dry summer (1990), the between-slope differences in radiation, and air and ground temperatures were exaggerated, while during the cloudy summer (1989), diffuse rather than direct solar radiation prevailed and the differential heating between slopes was reduced. Ground thaw increased in the warm summer, but maximum thaw depth at any site was also affected strongly by vegetation and soil characteristics, the latter being controlled by local geology and geomorphic processes. Precipitation on slopes can be influenced by wind and snow accumulation is modified by the local topography such as slope concavities. Snow ablation was largely accomplished through radiation melt so that the albedo changes were important. Meltwater runoff was maintained only downslope of deep snowbanks, and only the lower slopes experienced continuous saturation or groundwater flow. The spatial pattern of snow accumulation, frost table configuration, and surface or groundwater flows tend to recur annually, indicating the long-term influence of topography, soils, and vegetation on hydrologic processes at the local scale. Such studies linking the spatial and temporal variability of environmental attributes on energy and water flow improve our understanding of landscape ecology in northern environments and are useful when point observations are scaled up to match the dimensions of regional climate models.
Twenty-five thousand years ago, sea level fell more than 400 feet below its present position as a consequence of the growth of immense ice sheets in the Northern Hemisphere. A dry plain stretching 1,000 miles from the Arctic Ocean to the Aleutians became exposed between northeast Asia and Alaska, and across that plain, most likely, walked the first people of the New World. This book describes what is known about these people and the now partly submerged land, named Beringia, which they settled during the final millennia of the Ice Age. Humans first occupied Beringia during a twilight period when rising sea levels had not yet caught up with warming climates. Although the land bridge between northeast Asia and Alaska was still present, warmer and wetter climates were rapidly transforming the Beringian steppe into shrub tundra. This volume synthesizes current research-some previously unpublished-on the archaeological sites and rapidly changing climates and biota of the period, suggesting that the absence of woody shrubs to help fire bone fuel may have been the barrier to earlier settlement, and that from the outset the Beringians developed a postglacial economy similar to that of later northern interior peoples. The book opens with a review of current research and the major problems and debates regarding the environment and archaeology of Beringia. It then describes Beringian environments and the controversies surrounding their interpretation; traces the evolving adaptations of early humans to the cold environments of northern Eurasia, which set the stage for the settlement of Beringia; and provides a detailed account of the archaeological record in three chapters, each of which is focused on a specific slice of time between 15,000 and 11,500 years ago. In conclusion, the authors present an interpretive summary of the human ecology of Beringia and discuss its relationship to the wider problem of the peopling of the New World.
:Putu, discovered nearly thirty-five years ago, remains one of only a few Alaskan sites with fluted points in an excavated context, possibly associated with radiocarbon dates. The potential importance of Putu cannot be disputed, for it also contains other technologies possibly Pleistocene in age, like blades and lanceolate points. This paper presents the results of a reanalysis of the artifact assemblage and its spatial context. The study shows that Putu probably contains at least three components: 1) a Mesa complex Paleoindian component dated to ca. 10,500 radiocarbon years B.P.; 2) a fluted point component, possibly associated with blades and, while essentially undated, very tentatively linked to dates of ca. 8,500 radiocarbon years B.P.; and 3) an historical era component. Making use of detailed provenience data from the original excavations, the reanalysis also demonstrates extensive post-depositional disturbance of the site, which places severe limits on the conclusions that can be drawn. As a result, interpretations of the site must be viewed with caution.
Twelve profiles of alpine soils associated with well-developed, but currently inactive, sorted polygons were investigated in the Uinta Mountains of northeastern Utah. The summit upland in the Uintas does not appear to have been glaciated, and these soils are considerably older than those located in lower elevation glacial valleys. Profiles of soils from the polygon centers reveal a dark, organic-rich surface horizon developed in loamy loess overlying a series of redder, sandy B horizons locally exhibiting strongly developed platey structure and pockets of coarser sediment. Irregular and broken horizons at depth reflect extensive cryoturbation during episodes when the sorted polygons are active. Overall morphology and profile quantities of weathering products in these soils are similar to those previously reported for alpine tundra soils in the Uintas; however, the cryoturbated horizons are limited to soils in the patterned ground. A developmental model for these soils emphasizes the combined role of pedogenic processes operating during interglaciations (accumulation of organic matter and loess, translocation of silt and clay, chemical weathering) and periods of cryoturbation (distortion of horizons, redistribution of weathering products within the solum). Outstanding questions include the timing and relative duration of cryoturbation episodes, the timing of loess deposition, and the overall age of the soils.
In recent years archaeologists and paleontologists have become increasingly interested in how and why vertebrate animal remains become, or do not become, fossils. Vertebrate Taphonomy introduces interested researchers to the wealth of analytical techniques developed by archaeologists and paleontologists to help them understand why prehistoric animal remains do or do not preserve, and why those that preserve appear the way they do. This book is comprehensive in scope, and will serve as an important work of reference for years to come.
The depth to permafrost, thickness of the surface organic layer, and strength of redoximorphic features are closely correlated in soils on low-relief bedrock hills and colluvial slopes near Hughes, Alaska. Soils can be arrayed along a morphological gradient from warm-dry-mineral to cold-wet-organic, and the ranks of soils along this gradient correlate with topographic parameters and mineral soil texture. The warm-dry-mineral soils tend to occur on coarse-textured materials, convex slopes, steep slopes, and south-facing slope aspects, while the cold-wet-organic soils tend to occur on fine-textured materials, concave slopes, gentle slopes, and north-facing aspects. Slope shape and mineral soil texture are the geomorphic factors most closely associated with the ranking of soils along the morphological gradient from warm-dry-mineral to cold-wet-organic.
Radiocarbon dates for the terminal Pleistocene are about 2,000 years too young. Furthermore, because of significant carbon perturbations that are manifest as plateaus or abrupt jumps in age, radiocarbon dates of ca. 12,500 to 10,000 B.P [14C] must be critically evaluated. The first successful human colonization of the Americas occurred not 11,500 but about 13,500 years ago. This basic chronological revision has important implications for models of Paleoindian colonization, population expansion, and genetic and linguistic divergence.
Coastal erosion plays an important role in the terrestrial–marine–atmosphere carbon cycle. This study was conducted to explore the spatial variation of soil organic carbon (SOC) and other soil properties along the coastline of northern Alaska. A total of 769 soil samples, from 48 sites along over 1800-km of coastline in northern Alaska, were collected during the summers of 2005 and 2006. A geological information system (GIS) and a geostatistical method (ordinary kriging) were coupled to investigate the spatial variation of SOC along the coastline. SOC have a big variation ranging from 0.8 to 187.4 kg C m− 2 with the greatest value observed in the middle and lowest in the northeastern coastline. Compared to the 1-D model or the 1-D model with shortcut distance, the 2-D model was more reasonable to describe SOC along the coastline. The Gaussian correlation structure model had less prediction error than other examined geostatistical models. All mapping results also indicate that soils of the northwestern coastline stored greater SOC than those of the northeastern coastline. The estimation of total SOC along the coastline of northern Alaska was 6.86 ∗ 107 kg m− 1. The prediction errors indicated that greater errors were observed in both ends of the coastline than were observed in other fractions, although the range was from 0.739 to 0.779. Our study suggests that the isotropic 2-D model without a trend, with the nugget effect and the Gaussian correlation structure is a useful tool to investigate SOC in large scale. Results of stable isotope of organic matter indicate that SOC are mainly derived from C3 plant, which ranged from − 30‰ to − 22‰.
Late Wisconsin paleobotanical and fossil insect data from the central and northern sectors of the Bering Land Bridge indicate widespread mesic shrub-tundra environments even during the last glacial maximum. Vegetation before the last glacial maximum was a birch-heath-graminoid tundra with few or no steppe elements. Shrubs were not an important element of the vegetation, but were present in small numbers. During the interval 20,000–14,000 yr BP, land-bridge vegetation was dominated by birch-graminoid tundra with small ponds containing aquatic plants. Heaths were relatively unimportant. Insects from this interval were indicative of arctic climate, with drier tundra than during the late glacial. During the late-glacial interval (14,000–11,000 yr BP), land-bridge vegetation was dominated by birch-heath-graminoid tundra with small ponds choked with aquatic plants. The insect record indicates open-ground habitats dominated by mesic tundra. By 11,000 yr BP, insect data suggest that summer temperatures on the emergent Bering Shelf were warmer than present-day upland regions in western Alaska; summer temperatures on the Chukchi Shelf were warmer than the present-day North Slope of Alaska. Contrary to previous hypotheses, we found no evidence of steppe-tundra on the land bridge. New accelerator mass spectrometer (AMS) 14C dates show that much of the land bridge was above sea level and thus available for human and animal migration until as late as 11,000 yr BP.
Many of the physical and biological processes that characterize arctic ecosystems are unique to high latitudes, and their sensitivities to climate change are poorly understood. Stratigraphic records of land–surface processes and vegetation change in the Arctic Foothills of northern Alaska reveal how tundra landscapes responded to climatic changes between 13,000 and 8000 14C yr BP. Peat deposition began and shrub vegetation became widespread ca. 12,500 14C yr BP, probably in response to the advent of warmer and wetter climate. Increased slope erosion caused rapid alluviation in valleys, and Populus trees spread northward along braided floodplains before 11,000 14C yr BP. Lake levels fell and streams incised their floodplains during the Younger Dryas (YD) (11,000–10,000 14C yr BP). A hiatus in records of Populus suggest that its geographic range contracted, and pollen records of other species suggest a cooler and drier climate during this interval. Basal peats dating to the YD are rare, suggesting that rates of paludification slowed. Immediately after 10,000 14C yr BP, lake levels rose, streams aggraded rapidly again, intense solifluction occurred, and Populus re-invaded the area. Moist acidic tundra vegetation was widespread by 8500 14C yr BP along with wet, organic-rich soils. Most of these landscape-scale effects of climatic change involved changes in moisture. Although low temperature is the most conspicuous feature of arctic climate, shifts in effective moisture may be the proximate cause for many of the impacts that climate change has in arctic regions.
The Bering Land Bridge (BLB) connected the two principal arctic biological refugia, Western and Eastern Beringia, during intervals of lowered sea level in the Pleistocene. Fossil evidence from lowland BLB organic deposits dating to the Last Glaciation indicates that this broad region was dominated by shrub tundra vegetation, and had a mesic climate. The dominant ecosystem in Western Beringia and the interior regions of Eastern Beringia was steppe–tundra, with herbaceous plant communities and arid climate. Although Western and Eastern Beringia shared many species in common during the Late Pleistocene, there were a number of species that were restricted to only one side of the BLB. Among the vertebrate fauna, the woolly rhinoceros was found only to the west of the BLB, North American camels, bonnet-horned musk-oxen and some horse species were found only to the east of the land bridge. These were all steppe–tundra inhabitants, adapted to grazing. The same phenomenon can be seen in the insect faunas of the Western and Eastern Beringia. The steppe–tundra beetle fauna of Western Beringia was dominated by weevils of the genus Stephanocleonus, a group that was virtually absent from Eastern Beringia. The dry-adapted weevils, Lepidophorus lineaticollis and Vitavitus thulius were important members of steppe–tundra communities in Eastern Beringia, but were either absent or rare in Western Beringia. The leaf beetles Chrysolina arctica, C. brunnicornis bermani, and Galeruca interrupta circumdata were typical members of the Pleistocene steppe–tundra communities of Western Beringia, but absent from Eastern Beringia. On the other hand, some steppe tundra-adapted leaf beetles managed to occupy both sides of the BLB, such as Phaedon armoraciae. Much of the BLB remains unstudied, but on biogeographic grounds, it appears that there was some kind of biological filter that blocked the movements of some steppe–tundra plants and animals across the BLB.
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